Abstract: Schemes of the downstream products of methanol were optimized by the theory of system engineering and a comprehensive evaluation model involving technology，economics，and market aspects was established by using analytic hierarchy process (AHP) to calculate，analyze，and appraise the schemes of the downstream products of methanol. The conclusion showed that the most ideal product scheme for a coal based 1.8 Mt/a methanol project was to match a 1.2 Mt/a dimethyl ether (DME) project and an effective method was provided for scheme optimization of the downstream products of methanol.